Indicating dial for photoelectric light meters



Nov. 7, 1950 l R. D. HlcKoK 2,529,337

INDICATING DIAL FOR PHOTOELECTRIC LIGHTn METERS Filed Feb. 15, 1947 /NvENroR Rau-Rr D. H/cnax l1- 27. El @7d/WM www ATTORNEYJ Patented Nov. 7, 1950 F UNIT-'Eo STATES; or Flor-:i

INDICATING'DIAL FOR PHOTOELECTRICr LIGHT METERS" RobertrrD. .f Hickokyratenahl, Ohio, assignor; rto Cleveland Patents,"Y Incorporated; l, Cleveland, Ohio, a corporation of Ohio Application Februaryf15, 1947, SrialNL728g914i Y 5 ClaimsV (Cl. 235Q-64.3)

The` inventionielates. to! photographic: exelectricfexposureV meter,v whereon ltheiindicatedlfposurefmeters andmoreparticularly to meters in scaledivisionscanhe. of greater cir'cumferentialz-Y which a pointer moves to various positions-'over a i extentl than Aquantitatively comparable' scale vdi-zscale', :the pointer being responsive tolvariations visions onfother meters, by-reasonfof'the greater 3 infthe-intensitvof light strikinga light:sensitivi-:fv 5M total circumferential angular span of the come' cell i of the-photoelectric type. plete scale vasl aforesaid.

The invention isA` more particularly concerned. A-further object of-y the invention is'to ,provide-r with theicharacter, of-'the Scales associatedwith nove'land improvedscaleemeans for a photoelecfthe-pointer, and `also' 'with the angular extent ofiv tricexposure.ineterfzwherein'the increasedfsca'lef'V the sca-les @as adetermined-.from'the axis:of swing s, maxlength" permits the use oran-increasednumberr-of:i of. the pointerI asf a center; scale markings, and consequently permits@ greater:-

Inmetersof the...photoelectric'type heretofore'.' precision in actually indicating? SubedVSiOIiS available, thesscalef indicatingi light-intensity; on; Without the heeesstyi of nterpolatiompr lestimaefother factors did nottoccupya circumferential.: tionpffthei same.- extent-oi-morerthan 180 degreesfof ldia1face1,-iand 15 A further-'objecteofthe invention is to provide actually represented: ana arc z of. :noti more: than novel-andfimproved scale means. fora ph'0t`0e1ec-'- onefzhundred degrees Withz. reference'. toxthezi axis f; tric fexposure.-rneterzwhereinrv all necessaryy scales: ofl swingl; ofiv an indicating; pointer; since such. are-Carried Orl juxtaposed Concentlic'rstrips orapgpointer was usually/1,; offsetfrom-the uialrcenterr proximately. the Same arcuate extentandofthe- Thisr angular. limitation restricted.. the'A actual 2o sameorentaton With respect tothe observent-swlength of the-scalegandmaderitdifculttofproe thaty any andra-11 Scalesfare'rIIOrefeaSily readable f vide ;an:adequate number of marke'clfscale incre than inlightfmeters:wherein a`I numberrfofnd ments,lor subedivisionsy of the ,complete sca-le.v abutting scale-strips occupythe completezecire' Further; Vin previously available photoelectric Cumflerltal periphery 0f the dialfa'ce: metersithe complete-:dial was usually used; theH 25 Other Objects and advantages willbe-apparent top 13o-degrees Carrying; one; or morefscales/for from vthe follow-ing-description, in' conjunction different .efactora-v and` Vthe -bottom 180 degrees" with the laccompanying Ldrawings illustratingfoneV likewise carrying one or morescalesV ,forxotheri embOdmehUOf the rlVerlfOrrn Which factors, these latter sca-les heingfof coursefarcw Fig. lois a top` plan view of a meter "housing atelye reversed.` Sometimes even the rearof the-11 30 and dial, the ShOWihgberl'g-Semewhat larger-thani meter housingcarriedfixed or movahlereference the-aotualsize ofa conventional meter. scales. or tables: This vvas a::fruitful:'sourceaofi: Fg.42 is va-sectionalview-'of :thedial face,v taken confusion in readingthe meter; particularlywhen 'z approximately on the line 2*-2 of Fig'. 1. dialrotation or manipulation Wasrequired as raf Fig..3 Ais -a fragmentaryportion, somewhaten; pre-requisite to .ndingthe ultimate informati'ong35 1a.rged, of. the dialface shown inliigrl, the dial desired pointerbeingfin a dilferent'positi'on.f

An` object of the invention.; is. to provide :novel The light7 sensitive and light responsive zmeter and improved scale means for `an.exposuremeterrparts such as a photoelectric cell,slma'gnets`; of -therphotoelegtric type,V the light intensity in'- DArsonval coil,rand associated working elements dicating pointer being swingable circumierential 40 `may -be'iofvanyvsuitable design, although'fit will; ly through a scalespanof materially morethan't` be apparentk as-the description proceeds that ther onefhundred degrees around a center coincident indicating dial h'ere'rshown isespecially' adapted with the Vaxis of rotation ofthe indicatingpointer.-` for use-With a so-called ;tWo hundred and fifty.

A further object of the inventionis--to provide degreeswing meter'movement of the particularz' novel .and improvedscale meansl ofthe character 45 structuremore fullyl described' and-,illustrated :in:`

described wherein Vall indicating scalesincluding myco-pending application; Serial* :No 72'8,9:1\3; thosefor lm speed, shutter speed, .and irisA difiled` concurrentlyherewith. For0 simplicity; aphragm opening (generally termed lensstop@` therefore I show onlythe-indicatingfdiaL among-g opening) .extend concentrically in adjacent end-l ventional` pointenaand fragmentary/portionsoff mutually.. registrableparallel:arcs through aseg- 50i the pivotaxis, the coil, andthe cor-e;

mentalspan of materially more thanonehundred Reference character i@ indicates'a housingsutr. degrees.l around a center coincidentwiththeaxis,-v ablezfor the reception of-theaioresaid light sen'sifh of rotation of the indicating pointer. Y tive and. 1ight,1-esponsve parts., An .indicatng.

A` further object oi. the invention-istoprovdeU pointerill swlngsonan axis :I 2-:1resp0nsiyefw the-g, novel andimproved scalemeans rfor-Ya .photo 5.5 movement ofeaDArsonvalcoil I3'; around'al` corel.`

I3a in a magnetic field, the coil and core being indicated only fragmentarily (Fig. 2)

Carried on the housing, and disposed above the pointer Il is an indicating dial comprising an annulus I Il and a disk I which are superposed, and concentric with the pointer axis. The disk I 5 in the embodiment shown is fixed with respect to the housing I0. The annulus It is slidably rotatable above the disk I5 by means of a rotatable retaining ring I6. A glass cover plate Il is usually supplied, and is also rotatable with ring I6. The annulus I4 may be adhesively united to the glass Il, so that glass, annulus, and ring rotate as a unit. The ring is slidably rotatable in a groove Ia in housing lil, but is ordinarily not removable.

The disk I5 is provided with an arcuate slot I8 concentric with the axis of rotation of pointer I I, the slot permitting observation of the pointer position. The annulus lll is provided with an arcuate slot I9, also concentric with the axis of'.

rotation of pointer l l. The slot i9 permits observation of an underlying arcuate portion of disk I5.The disk l5 and the annulus lli carry correlatable scales, the registering relationships between which may be changed by relative movementbetween the disk and annulus. Movement of pointer i l responsive to light striking the photoelectric cell (not shown) evaluates an additional factor, namely, the intensity of the light being measured and indicated.

vThe character and relationship of the several scales will' now be kmore speciiically described. It is understood, of course, that the user-of -aphotoelectric light meter "is p-rimarily interested in determining the proper combination of shutter speed and lens stop aperture to be used in making a photographic exposure, having due regard for the existing light intensity. lt is further understood that it is highly desirable thatvthe meter be easy to read and that required meter manipulations be reduced to an absolute minimum, so that the photographer may concentrate on the taking of the picture. y

Disc I5 carries thereon an arcuate strip 2G of scalev indicia for time increments, immediately beneath and registrable with slot le, and representing camera shutter speeds in seconds and fractionsthereof. The individually marked scale divisions, such as 1, S/i, 1/2 etc., are alternately black and white, for ease in selection. The designations lFPS and SZFPS on the same scale refer to frames per second, a marking signicant to users of motion picture cameras.

For convenience this strip 2Q may be termed the time scale. Since it iscarried on the disc I5 which is xed with respect to the housing, and l with respect. tothe pointer swing, it will be ob# vious that motion of the pointer forwardly or rearwardly along the time scale likewise indicates progressive increase or decrease of light intensity, and that the said time scale might also have been marked with progressive indicia representing light value units. As will appear such marking is unnecessary for normal use of the present meter since the pointer indicates directly on another associated scale the ultimate information usually desired. It may be borne in mind however that the marked time increments'on the time scale are actually inversely proportional to correspondingA variations in light intensity. For example, the markings 4 and 2 on the time scale, represent fourseconds and two seconds shutter speed, andlikewis'e indicate that When theA pointer moves from4 ,;to 12, the actinic value of the light has 4 doubled, thereby permitting the exposure time to be halved.

One distinct advantage of the present indicating dial is that no separate light intensity scale is required, its function being combined with, and integrated in, the time scale. Troublesome translation of light values from one scale to another is thereby avoided.

Annulus I4 carries thereon two arcuate strips of scale indicia 2I and 22, one strip on each side of the slot I9, so as to be mutually registrable with the time scale 2KB above mentioned. Scale 2| indicates film sensitivity, usually termed lm speed, the markings conforming to any accepted standard. More than one such set of markings may of course be juxtaposed on the iilm speed scale 2 I. Scale 22 indicates lens aperture, the markings conforming to any accepted standard, such as the f stops commonly used on the controls for present day iris diaphragms for camera lenses.

It will be observed thatthe three scales 20, 2l and.22 are juxtaposed in three arcuate strips,

concentric with the axis l2 of the pointer swing-f and all uniformly oriented for ease in comparison and scale reading, and that they extend around a major portion of the meter dial to an angular extent of approximately two hundred and fifty degrees.

will soon appear, the meter is of the direct reading type, the pointer indicating the ultimate information directly, without further manua operation or mental calculation. f

In operation the ring IB is rst turned until the sensitivity value of the lm being used, for example 25 on scale' 2 I, Fig. 3 is in registry with the shutter speed intended to be used, for example one-iiltieth of a second on scale 20. The light acceptance aperture 25 of the meter is then pointed at the object or Zone'to be photographed.

Pointer Il thereupon swings to a position corresponding to the light intensity of the angular eld scanned by aperture 25. In so doing'the v.pointer also indicates, on scale 22, the particular lens stop opening to be used to obtain the proper exposure in View of the existing light intensity,v

for example f stop I I.

The ease and simplicity of use of the meter scale just described will be immediately apparent. y

the camera is loaded with film, there is no further y manual operation, or mental calculation, or meter manipulation required other than to actually point the meter'at the object to be photographed,

60'. or the brightness of which is to be determined.

The extension of the scale strips to an angular Y, span of more than two hundred degrees permits the use of a much greater number of individually marked scale increments, so that whereas it was' "i formerly necessary to estimate certain inter# mediate'shutter speeds or lens stops, such intermediate speeds and stops may now be actually u marked, plainly seen, and definitely indicated as.

Of course be realized, though to a'somewhat less if It will be further observed that theremaining angular span of the dial containsno` scales or other necessary reference data, and, as

obvious extent, with meters wherein the pointer swing is less than two hundred and fifty degrees, but more than the conventional ninety or one hundred degrees.

What I claim is:

1. An indicating dial for a light meter of the character described wherein a pointer swings on a pivotal axis responsive to variations in light intensity, said dial including a rst scale with which said pointer is registrable, and sub-divided into increments representing time periods, and proportional to respective quantitative increments of light intensity, a second scale subdivided into increments representing respective lens stop openings, and a third scale movable as a unit with said second scale, and subdivided into increments representing photographic film sensitivity means for producing relative movement between said first and second scales, all three said scales being segmental in character and being juxtaposed in three arcs of successively decreasing radii, all said arcs being concentric with respect to said pivotal axis, each said scale extending around a major portion of the circumferential extent of the dial.

2. An indicating dial for a light meter of the character described wherein a pointer swings on a pivotal axis responsive to variations in light intensity, said dial including a rst scale with which said pointer is registrable, and sub-divided being segmental in character and being juxtal posed in three arcs of successively decreasing radii, all said arcs being concentric with respect to said pivotal axis, each said scale extending for approximately two hundred and fifty degrees around said dial with relation to the axis of swing of said pointer.

3. An indicating dial for a light meter of the character described wherein a pointer swings on a pivotal axis responsive to variations in light intensity, said dial comprising superposed upper and lower scale carrying members, means for permitting relative rotation between said members around a center coincident with said pivotal axis, said lower scale carrying member having on its upper surface an arcuate time scale graduated in seconds and fractions thereof, said upper scale carrying member having therein an arcuate slot registrable with said time scale whereby said time scale is visible through said slot, said upper scale carrying member having on its upper surface a lens stop scale of arcuate form adjacent one edge of said slot, and a lm sensitivity scale of arcuate form adjacent the other edge of said slot, said lens stop scale and said lm sensitivity scale being immovable with respect to each other but both being movable with respect to said time scale, all three said scales being registrable with 6 pointer swing and being concentric with respect to the said pivotal axis, and the angular extent of each said scale being substantially in excess of one hundred degrees with respect to said axis.

4. An indicating dial for a light meter of the character described wherein a pointer swings on a pivotal axis responsive to variations in light intensity, said dial comprising superposed upper and lower scale carrying members, means for permitting relative rotation between said members around a center coincident with said pivotal axis, said lower scale carrying member having on its upper surface an arcuate time scale graduated in seconds and fractions thereof, said upper scale carrying member having therein an arcuate slot registrable with said time scale whereby said time scale is visible through said slot, said upper scale carrying member having on its upper surface a lens stop scale of arcuate form adjacent one edge of said slot, and a film sensitivity scale of arcuate form adjacent the other edge of said slot, said lens stop scale and said film sensitivity scale being immovable with respect to each other but both being movable with respect to said time scale, all three said scales being registrable with pointer swing and being concentric with respect to the said pivotal axis, each said scale extending around a major portion of the circumferential extent of the dial.

5. An indicating dial for a light meter of the character described wherein a pointer swings on a pivotal axis responsive to variations in light intensity, said dial having three juxtaposed arcuate scale strips each registrable with pointer swing and denoting, respectively, time indicia, film sensitivity indicia, and lens stop indicia, the film sensitivity indicia scale and time indicia scale being movable with respect to each other to vary the registrable relationship between their respective indicia, all three said scales lying in parallel strips concentric with respect to said pivotal axis, and being similarly oriented with respect to a single observing position so as to be easily observable and readable from said position, each said scale extending around a major portion of the circumferential extent of the dial, said pointer being adapted to directly indicate the lens stop to be used for the existing light intensity when the sensitivity index of the film being used is placed in registration with the specific shutter speed time index.

ROBERT D. HICKOK.

REFERENCES CITED The following references 'are of record in the file of this patent! UNITED STATES PATENTS Number Name Date 2,147,999 Tonnies Feb. 21, 1939 2,394,835 Arant 1 Feb. 12, 1946 2,421,504 Hickok June 3, 1947 FOREIGN PATENTS Number Country Date 430,073 Great Britain June 4, 1935 

